Method for calendering a fibrous web and a calender

ABSTRACT

A calender includes at least two roll stacks which each have at least three rolls, and in each of which the web path of a fibrous web meanders between each roll pair of the stack. In order to produce a selectable fibrous web grade, the web is passed between each roll pair of each stack, so that at least one roll pair in at least one stack is in nip contact to form a nip that calenders the web. The web runs between each roll pair of each roll stack and, in order to produce a selectable fibrous web grade, a selectable number of rolls is in nip contact with each other in each stack to form at least one nip that calenders the fibrous web.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national stage application of InternationalApp. No. PCT/FI2003/000961, filed Dec. 16, 2003, the disclosure of whichis incorporated by reference herein, and claims priority on Finnish App.No. 20030003, Filed Jan. 2, 2003.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to paper, pulp, board or other similarfibrous web machines. More specifically, the present invention relatesto calenders of fibrous web machines and, in particular, the presentinvention relates to a method for calendering a fibrous web in acalender which includes at least two roll stacks which each have atleast three rolls, and in which calender the fibrous web is passed torun between each roll pair of each roll stack. The invention alsorelates to a calender which includes at least two roll stacks which eachhave at least three rolls, and in which calender a fibrous web has beenpassed to run between each roll pair of each roll stack.

Calendering is a method by means of which attempts are generally made toimprove the properties of a web-like material, such as a paper web, inparticular, its thickness profile, smoothness, gloss, surface porosityand transparence. In the calendering process, a paper web is passed intoa nip formed between rolls pressed against each other, in which nip thepaper web is deformed due to the effect of temperature, moisture and nippressure, whereby the physical properties of the paper web can beaffected by regulating the above-mentioned parameters and the time ofaction. The good physical properties achieved by calendering result inimproved print quality, thus giving a competitive advantage to the papermanufacturer.

Up to the mid 1990s, calenders comprised three main categories, whichare typically single- or double-nip hard-nip calenders and softcalenders as well as multi-nip supercalenders. All these calender typeshave their advantages and disadvantages.

Shoe or so-called long-nip calendering has been found to be generallygood for producing low-gloss paper grades, i.e. grades having a Huntergloss % below 40. When a higher gloss is required, the nip pressure is,however, not sufficient to produce gloss. With continuously increasingrunning speeds, calendering is becoming a bottleneck in the papermakingprocess and adequate quality is not achieved by means of today'shard-nip calenders. The drawbacks of today's papermaking process alsoinclude the fact that the loss of bulk increases when gloss is improvedand that to achieve adequate quality it is necessary to employabundantly coated webs and/or use off-line calendering, in particularsoft calendering and/or multi-nip calendering, whose known applicationis supercalendering. The direction in the processing of the fibrous weband thus also in calendering is, however, towards on-line arrangementsto an ever-increasing degree, also when the intention is to producehigher-quality printing paper grades, such as SC and glossy coatedpapers. FIG. 2 illustrates with a broken line currently availabledifferent paper grades, which include, among other things,

-   -   NP (NewsPrint) newsprint paper grades,    -   SC (SuperCalendered) paper grades,    -   MFC (Machine Finished Coated) fine paper grades,    -   LWC (Light Weight Coated) paper grades, and    -   WFC (WoodFree Coated) fine paper grades,        and today's calenders, which include    -   a hard-nip i.e. machine calender,    -   a soft calender, and    -   a supercalender        for producing different paper grades. It can also be seen from        FIG. 2 that a multi-nip supercalender is remaining as the only        alternative when the aim is to manufacture high-quality, i.e.        high-gloss and smooth, WFC, LWC and SC paper grades.

The good characteristics of the calendering technique common today arebeginning to reach their physical limits and the surface properties ofthe fibrous web cannot be much improved any more without a risk of thesurface being scratched. When running speeds simultaneously increase tobe as high as 1600 m/min or more, a drawback is the shortening time ofaction of calendering, which leads to considerable capacity problemswhen producing high-quality paper grades, so that even threesupercalenders are not necessarily sufficient to produce high quality athigh speeds, but even a fourth supercalender is needed, which isexpensive both as an investment and in respect of operation.

Because of the development of the soft calender technology,polymer-coated rolls can be used in the calender today. A problemassociated with this is, however, that if more than three rolls in thesupercalender are provided with an elastic polymer coating, the qualityof the fibrous web begins to deteriorate. To meet increasing qualityrequirements, three new calender types have been developed, which arethe OptiLoad® calender developed by Metso Paper, Inc., provided with asingle roll stack and typically including 6-12 rolls and having as aspecial feature the possibility of affecting the linear loads ofindividual nips and providing the roll stack with a nip load eveninversely increasing with respect to the force of gravity; the Janus®calender developed by Voith-Sulzer, provided with two roll stacks andtypically including 6-10 rolls; and the Prosoft® calender developed byKüsters-Beloit, provided two roll stacks and typically including 6-14rolls.

These new type of multi-nip calenders, which can be used both as on-lineand off-line calenders, are standard types in today's calenderingtechnique and they are based on enhanced utilization of an elastic rollcoating, but they differ substantially from one another in respect ofattainable calendering results.

SUMMARY OF THE INVENTION

One object of the present invention is to reduce the weaknesses,drawbacks and problems associated with the known calendering techniqueand provide a novel calender which makes it possible to produce afibrous web within a broader range of gloss and smoothness without aneed for threading of the fibrous web and/or for shutdown of the fibrousweb machine, i.e. to make it possible to change the grade of the fibrousweb produced in on-line operation.

This object is achieved by means of the method and the calender of theinvention mentioned at the beginning, which method is generallycharacterized in that in order to produce a selectable fibrous webgrade, at least one roll pair in at least one roll stack is arranged tobe in nip contact to form a nip that calenders a fibrous web.

In accordance with an advantageous embodiment of the method inaccordance with the invention, at least one roll pair in each roll stackis arranged to be in nip contact to form in each roll stack at least onenip that calenders a fibrous web.

By means of the method in accordance with the invention, by increasingthe number of closed i.e. calendering nips in the calender it ispossible to produce higher-quality paper grades, such as SC-A, SC-B, LWCand WFC grades, and by decreasing the number of closed i.e. calenderingnips in the calender it is possible to produce lower-quality papergrades, such as NP, SC-C and/or MFC grades.

The aim of the invention is also achieved by means of the calendermentioned at the beginning, which calender is generally characterized inthat in order to produce a selectable fibrous web grade, at least oneroll pair in at least one roll stack has been arranged to be in nipcontact to form at least one nip that calenders a fibrous web.

An advantageous embodiment of the calender in accordance with theinvention is characterized in that in order to produce a selectablefibrous web grade, at least one roll pair is in nip contact in each rollstack, whereby at least one nip that calenders a fibrous web is formedin each roll stack.

The invention can be employed to produce fibrous webs of differentgrades and to change the grade of the fibrous web during running in anycombination of rolls. Advantageous calenders for applying the inventionare, among other things, various multi-roll-stack calenders, such as,for example, OptiLoad®, Janus® and Prosoft® calenders. In thatconnection, it is to be recommended that the roll combination in twosuccessive roll stacks of the calender is, for example, 2×3, 2×5, 2×7,3+5, 5+5, 5+7.

As all rolls in the calender in accordance with the invention aremovable with respect to each other, a fibrous web can be calendered onthe calender while all nips are operating, in which connection all rollgaps in each roll stack of the calender are closed and form a closednip, or while one/some of the nips is/are operating, in which connectionat least one roll gap in at least one roll stack is open, i.e. a nipthat does not calender the fibrous web. In that connection, differentpaper grades, such as NP, SC, MFC, LWC and WFC grades can be produced byregulating the number and/or nip load of closed i.e. calendering nips.Particularly advantageously, operation with one/some of the nips issuitable for the production of lower-quality paper grades, such as NP,SC-C and MFC grades, and operation with all nips is suitable for theproduction of high-quality paper grades, such as SC-A, SC-B, LWC and WFCgrades.

In accordance with the invention, for moving rolls at least one rollstack of the calender includes power means arranged between carrierarms, support arms or bearing housings of roll pairs formed by rollsplaced one upon the other in order to adjust nip load and/or to form anopen nip and/or to form a closed nip between a roll pair by moving therolls of the roll pair in a direction substantially away from each otheror towards each other.

With respect to the advantages of the invention it may be mentioned thatcalendering capacity can be improved by the possibility of creating anon-line process line using a single calender arrangement for producingdifferent grades, as an example of this can be mentioned a process linethat makes it possible to produce fibrous webs of different grades, suchas a paper web whose grade can be selected between the grades newsprint. . . SC-A. An advantage is also that the fibrous web production lineneed not be stopped for the duration of maintenance of the calender. Inthat case, in on-line operation it is possible to replace, for example,a soft roll with a thermo roll or vice versa, thus achieving a differentcalender in respect of its production characteristics.

In the following, the invention will be described by way of example bymeans of one advantageous embodiment of the invention, which isaccomplished in Metso Paper, Inc.'s OptiLoad® calender, with referenceto the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a calender comprising two roll stacks,such as, for example, an OptiLoad®, Janus® or Prosoft® supercalenderhaving two roll stacks, to make use of the present invention.

FIG. 2 illustrates paper grades attainable by means of ordinary knowncalendering techniques and paper grades attainable by the method and thecalender in accordance with the invention in a system of Huntergloss/smoothness coordinates.

FIG. 3 shows one embodiment for moving the rolls of one roll pair in thecalender with respect to each other.

FIG. 4 shows a second embodiment for moving the rolls of one roll pairin the calender with respect to each other.

FIG. 5 shows a third embodiment for moving the rolls of one roll pair inthe calender with respect to each other.

FIG. 6 shows a fourth embodiment for moving the rolls of one roll pairin the calender with respect to each other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic view of a supercalender 10 provided with two rollstacks. Hereafter the supercalender provided with two roll stacks isreferred to by the definition calender 10 for the sake of simplicity.The calender 10 shown in FIG. 1 includes two roll stacks 11L, 11R. Inboth roll bodies of the calender, a top roll 1, a bottom roll 5 and acenter roll 3 are soft rolls having an elastic shell and a thermo roll2, 4 having a hard-surface shell is arranged between the top roll 1 andthe center roll 3 as well as between the bottom roll 5 and the centerroll 3.

In the calender 10 of FIG. 1, a fibrous web W runs in both roll stacks11L, 11R, between which the travel of the web is guided by a guide roll16, meandering between each roll pair 1, 2; 2, 3; 3, 4; 4, 5 aroundspreader rolls 15 of the web. In both roll stacks 11L, 11R there arefour roll gaps NC, NO, one between each roll pair 1, 2; 2, 3; 3, 4; 4,5. In the embodiment of FIG. 1, a roll pair is formed of an elastic rolland a thermo roll. When the rolls of a roll pair are in shell contactwith each other, a nip NC that calenders the web is formed between therolls, and when the rolls of a roll pair are out of shell contact witheach other, a roll gap NO that does not calender the web W is formed.

In accordance with the basic idea of the invention, to produce aselectable fibrous web grade, at least one roll pair in at least oneroll stack is arranged to be in nip contact to form a nip that calendersthe fibrous web. In other words, in order to produce a selectablefibrous web grade, in the calender in accordance with the inventionthere is in at least one roll stack 11 at least one roll pair 1, 2 innip i.e. shell contact, whereby at least one nip NC that calenders thefibrous web is formed.

To form two nips NC that calender the web W, in the embodiment of FIG.1, the top roll 1 and the upper thermo roll 2 as well as the bottom roll5 and the lower thermo roll 4 are arranged to be in nip contact in theleft-hand roll stack 11L of the calender 10 by moving the rolls in thevertical direction, i.e. more generally in the direction of the rollstack. To form three nips NC that calender the web W, in the embodimentof FIG. 1, the top roll 1 and the upper thermo roll 2, the upper thermoroll 2 and the center roll 3, as well as the bottom roll 5 and the lowerthermo roll 4 are arranged to be in nip contact in the right-hand rollstack 11R by moving the rolls. In the calender 10 of the embodiment ofFIG. 1, the rolls 1-4 in both roll stacks 11L, 11R are movable by meansof loading or carrier arms 6. In addition, by means of the carrier arms6 it is possible to adjust the magnitude of the compression or loadingforce applied on the fibrous web by the nip NC between the rolls whichare in shell or nip contact. In the embodiment of FIG. 1, in both rollstacks 11L, 11R of the calender 10, the bottom roll 5 is loaded by ahydraulic cylinder 7 which is located underneath the bottom roll 5 andwhich advantageously acts in the same manner as the loading or carrierarms 6 on the non-rotating shaft of the roll or on the bearing housingsof the roll shell journalled to be rotatable on the shaft.

Reference is made to FIG. 3 showing one embodiment for moving the rollsof one roll pair of the calender with respect to each other, forexample, in the direction of the roll stack. In the embodiment of FIG.3, which is particularly suitable for Metso Paper, Inc.'s OptiLoad®calender, a power member 81, which is advantageously a hydraulic orpneumatic cylinder or a power screw, is disposed between the loading,support or relief arms 6 of the rolls, which arms turn in a lever-likemanner at one end thereof. When the length of the power member 81 isincreased, the loading, support or relief arms 6 turn in a lever-likemanner away from each other, whereby the nip load between the rolls ofthe roll pair 2, 3 is relieved or the rolls come out of shell contactand form an open nip NO of FIG. 3 that does not calender the fibrous webW. When the length of the power means 81 is shortened, the loading,support or relief arms 6 turn in a lever-like manner towards each other,whereby the nip load between the rolls of the roll pair 2, 3 increasesand the nip NC that calenders the fibrous web W is closed.

Reference is made to FIG. 4 showing a second embodiment for moving therolls of one roll pair of the calender with respect to each other, forexample, in the direction of the roll stack. In the embodiment of FIG.4, which embodiment like the embodiment of FIG. 3 is suitable inparticular for Metso Paper Inc.'s OptiLoad® calender, a power means 81,which is advantageously a hydraulic or pneumatic cylinder or a powerscrew, is disposed between the loading, support or relief arms 6 of therolls, which arms turn in a lever-like manner at one end thereof. Theembodiment of FIG. 4 differs from the embodiment of FIG. 3 in that theloading, support or relief arms 6 are connected by means of anarticulated joint 9 to form two parts. In this embodiment of FIG. 4, thepower means is arranged on a second part of the loading, support orrelief arms 6 on the side of the roll 2, so that a first part of theloading, support or relief arms 6 can be kept unmovable and non-turningabout its fulcrum point in a lever-like manner, which substantiallyfacilitates the locking of the loading, support or relief arms 6 in adesired orientation. When the length of the power means 81 is increased,the second parts of the loading, support or relief arms 6 on the side ofthe rolls 2, 3 turn in a lever-like manner away from each other, wherebythe nip load between the rolls of the roll pair 2, 3 is relieved or therolls come out of shell contact and form an open nip NO of FIG. 4 thatdoes not calender the fibrous web W. When the length of the power means81 is shortened, the second parts of the loading, support or relief arms6 on the side of the rolls 2, 3 turn in a lever-like manner towards eachother, whereby the nip load between the rolls of the roll pair 2, 3increases and the nip NC that calenders the fibrous web W is closed.

Reference is made to FIG. 5 showing one embodiment for moving the rollsof one roll pair of the calender with respect to each other. Theembodiment of FIG. 5 substantially corresponds in operation to theembodiment of FIG. 3 and is thus suitable for use in particular in MetsoPaper, Inc.'s OptiLoad® calenders. In this embodiment of FIG. 5, a powermeans 82 includes a wedge means that is movable by means of a hydraulic,pneumatic or a similar actuator to and fro, advantageously in adirection transverse to the center line passing through the center axesof the rolls of the roll pair 2, 3. In the embodiment of FIG. 5, thewedge means of the power means 82 acts between the loading, support orrelief arms 6 of the rolls such that when the wedge means is moved bymeans of the power means away from the roll pair 2, 3, the nip loadbetween the rolls is relieved or the rolls come out of shell contact andform an open nip NO of FIG. 5 that does not calender the fibrous web W,and such that when the wedge means is moved towards the roll pair 2, 3,the nip load between the rolls increases and the nip NC that calendersthe fibrous web W is closed.

In connection with the embodiment of FIG. 5 it must be noted that thewedge means can also be arranged to act between non-rotating shafts ofthe roll pair 2, 3 or between bearing housings of the rolls joumalled tobe rotatable, so that the embodiment is suitable for use in calenders inwhich the rolls 1-5 are not provided with loading, support or reliefarms 6, such as in Janus® and Prosoft® calenders.

Reference is made to FIG. 6 showing one embodiment for moving the rollsof one roll pair of the calender with respect to each other. In theembodiment of FIG. 6, which embodiment is suitable for use in calenderswhose rolls 1-5 are not provided with loading, support or relief arms 6,a power means 83 is arranged between the non-rotating shafts of the rollpair 2, 3 or between the bearing housings of the rolls joumalled to berotatable, which power means 83 is advantageously a hydraulic orpneumatic cylinder or a power screw. When the length of this kind ofpower means 83 is increased, the nip load between the rolls of the rollpair 2, 3 is relieved or the rolls come out of shell contact and form anopen nip NO of FIG. 6 that does not calender the fibrous web W. When thelength of this kind of power means 83 is shortened, the nip load betweenthe rolls of the roll pair 2, 3 increases and the nip NC that calendersthe fibrous web W is closed.

In connection with the invention it must be emphasized that the numberof the rolls in the roll stack 11L, 11R is not essential to the presentinvention. In accordance with the invention it is advantageous, however,that the roll combination of two successive roll stacks is selected fromthe group which includes 2×3, 2×5, 2×7, 3+5, 5+5 and 5+7 rolls. When thenumber of rolls is other than the five rolls shown in FIG. 1, i.e. nrolls, in the roll stack there are correspondingly more or fewer rollgaps than the four roll gaps of FIG. 1, i.e. n-1 roll gaps. Said rollcombination is provided, for example, by two successive roll stacks ofMetso Paper, Inc.'s OptiLoad® supercalender, by two successive rollstacks of Voith-Sulzer's Janus® supercalender or by two successive rollstacks of Küsters-Beloit's Prosoft® supercalender.

When the purpose of the calender in accordance with the invention is toproduce smoother and glossier paper qualities of different paper grades,such as WFC, LWC and SC paper grades, at least one roll pair 1, 2; 2, 3;3, 4; 4, 5 is arranged to be in nip contact in each roll stack 11L, 11Rand thus to form at least one nip NC calendering the fibrous web W ineach roll stack.

By means of the calender in accordance with the invention it is thuspossible to calender a fibrous web while all nips are operating or whileone/some of the nips is/are operating. When all nips are operating, allroll gaps in each roll stack 11L, 11R of the calender 10 are closedforming closed nips NC that calender the fibrous web W. A roll gap isclosed to form a web-calendering nip NC by moving the rolls of a rollpair 1, 2; 2, 3; 3, 4; 4, 5 defining the roll gap into shell i.e. nipcontact with each other, for example, in the direction of the rollstack. Operation with one/some of the nips operating differs fromoperation with all nips operating in that at least one roll gap in atleast one roll stack 11L, 11R of the calender 10 is an open roll gap ornip NO, in which the fibrous web is not calendered.

Reference is made to FIG. 2, which shows with a broken line the papergrade ranges which can be produced on known calenders and with anunbroken line the range which can be produced on the calender 10 inaccordance with the present invention. It is characteristic of theprior-art calendering technique that, as the starting point, a differentcalender type is intended for different paper grades. In accordance withthe present invention, many different paper grades, including NP, SC,MFC, LWC and MFC grades, can be produced by means of one and the samecalender of the invention, the type of said calender being asupercalender provided with at least two roll stacks, by regulating thenumber of the calendering nips NC, i.e. operation with all or one/someof the nips, and the nip load of the calendering nips NC. In thatconnection, operation with one/some of the nips is most suitable for theproduction of lower-quality paper grades, such as NP, SC-C and MFCgrades, and operation with all nips is favorably suitable for theproduction of high-quality paper grades, such as SC-A, SC-B, LWC and WFCgrades.

In summary of the invention it may thus be stated that, at the same timeas the present invention allows complete on-line or off-line operation,it is possible merely

-   -   by increasing the number of calendering nips NC in the calender        10 to produce higher-quality paper grades, and    -   by decreasing the number of calendering nips NC in the calender        10 to produce lower-quality paper grades.

Above, the invention has been described only by way of example by meansof one of its advantageous embodiments. By this it is, however, notdesired to limit the invention to such a single exemplifying embodimentand, as is clear to a person skilled in the art, many alternativearrangements and variations are feasible within the scope of protectionof the new and inventive basic idea defined in the appended claims.

Thus, it must be emphasized that the number of the roll stacks 11L, 11Rof the calender 10 may differ from the two roll stacks shown in FIG. 1and that the roll stack can in itself be formed of a roll order otherthan the roll order shown in FIG. 1, in which there are alternately softrolls and thermo rolls, so that to form a roll pair, the roll stack 11L,11R may comprise, for example two opposing thermo rolls, in whichconnection the roll pair can form a hard nip and the roll stack canserve as a hard-nip i.e. machine calender, or two opposing soft rolls,in which connection the roll pair forms therebetween a reversing nipthat does not calender the web W to calender the web on two sides in oneroll stack 11L, 11R.

1. A method for calendering a fibrous web in a calender which includes at least a first roll stack having three or five rolls, forming two or four pairs of rolls wherein the rolls of said roll pairs are movable with respect to each other in a direction defined by the first roll stack so as to form an open or closed nip, and a second roll stack having at least five rolls forming at least four roll pairs wherein the rolls of said roll pairs are movable with respect to each other in a direction defined by the second roll stack so as to form an open or closed nip, the method comprising the steps of: passing a fibrous web between each pair of rolls in the first stack and each pair of rolls in the second stack to form a threaded path; moving at least one pair of rolls from said first stack or said second stack to form at least one nip therebetween; producing a first grade of paper of selected PPS and selected Hunter Gloss % by calendering the web in the calender along the threaded path, followed by producing a second grade of paper of second selected PPS and second selected Hunter Gloss % along the threaded path by increasing or decreasing the number of nips formed by the calender.
 2. The method of claim 1, wherein at least one roll pair in each roll stack is arranged to be in nip contact to form in each roll stack at least one nip that calenders the fibrous web.
 3. The method of claim 1 wherein the paper web continuously passes along the threaded path while the first paper grade is changed to the second paper grade.
 4. The method of claim 1 wherein the rolls are arranged by increasing or decreasing the number of nips formed by the calender to produce a web with a Hunter Gloss % of less than 50% and a PPS of greater than 2 micrometers, followed by or preceded by production of paper grades with a Hunter Gloss % of greater than 50% and a PPS of less than 2 micrometers.
 5. The method of claim 1, wherein over time the rolls are arranged to produce paper webs within a range of a Hunter Gloss % from 30% to 91% and a PPS of 0.5 micrometers to 4.5.
 6. The method of claim 1, wherein the pairs of rolls of the first stack and the second stack are supported on support or relief arms which are movable with respect to each other; and further comprising the step of increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw positioned between the arms to open or close the pairs of rolls.
 7. The method of claim 1, wherein the pairs of rolls of the first stack and the second stack are mounted to support or relief arms; and further comprising the steps of holding the arms fixed and moving the pairs of rolls with respect to each other on articulated joints between the arms and said rolls, by increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw mounted between adjacent ones of said joints.
 8. The method of claim 1, wherein the rolls of the pairs of rolls of the first stack and the second stack are mounted to support or relief arms; and further comprising the step of opening or closing the pairs of rolls by moving a wedge between the arms of the roll pairs by increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw mounted between one of said arms and the wedge.
 9. The method of claim 1, wherein the rolls of the pairs of rolls of the first stack and the second stack have bearing housings to which the rolls are journalled to be rotated but are not provided with support or relief arms; and further comprising the step of increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw positioned between the bearing housings to open or close the pairs of rolls.
 10. A method for calendering a fibrous web in a calender which includes at least two roll stacks, including a first roll stack and a second roll stack, said first stack having three or five rolls, forming two or four pairs of rolls wherein the rolls of said roll pairs are movable with respect to each other, in a direction defined by the first roll stack so as to form an open or closed nip, and said second roll stack having at least five or seven rolls forming four or six roll pairs, wherein the rolls of said roll pairs are movable with respect to each other, in a direction defined by the second roll stack so as to form an open or closed nip, and in which calender the web is passed to run between each roll pair of each roll stack, the method comprising the steps of: disposing the rolls of each of the at least two roll stacks such that at least one roll pair is in nip contact to form a first nip; causing the web to pass through said first nip to calender the web; and adjusting the rolls of the at least two roll stacks to increase the number of nips through which the web passes to form a higher-quality paper grade, or to decrease the number of nips through which the web passes to form a lower-quality paper grade.
 11. The method of claim 10, wherein at least one roll pair in each roll stack is arranged to be in nip contact to form in each roll stack at least one nip that calenders the fibrous web.
 12. The method of claim 10, wherein the paper web continuously passes between each roll pair while the rolls are adjusted to form a higher-quality paper grade, or to form a lower-quality paper grade.
 13. The method of claim 10, wherein the rolls are arranged to produce a web with a Hunter Gloss % of less than 50% and a PPS of greater than 2 micrometers, followed by or preceded by the roll pairs being arranged for a production of paper grades with a Hunter Gloss % of greater than 50% and a PPS of less than 2 micrometers.
 14. The method of claim 10, wherein over time the rolls are arranged to produce paper webs within a range of a Hunter Gloss % from 30% to 91% and a PPS of 0.5 micrometers to 4.5.
 15. The method of claim 10, wherein the pairs of rolls of the first stack and the second stack are supported on support or relief arms which are movable with respect to each other; and further comprising the step of increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw positioned between the arms to open or close the pairs of rolls.
 16. The method of claim 10, wherein the pairs of rolls of the first stack and the second stack are mounted to support or relief arms; and further comprising the steps of holding the arms fixed and moving the pairs of rolls with respect to each other on articulated joints between the arms and said rolls, by increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw mounted between adjacent ones of said joints.
 17. The method of claim 10, wherein the rolls of the pairs of rolls of the first stack and the second stack are mounted to support or relief arms; and further comprising the step of opening or closing the pairs of rolls by moving a wedge between the arms of the roll pairs by increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw mounted between one of said arms and the wedge.
 18. The method of claim 10, wherein the rolls of the pairs of rolls of the first stack and the second stack have bearing housings to which the rolls are journalled to be rotated but are not provided with support or relief arms; and further comprising the step of increasing or decreasing the length of a hydraulic or pneumatic cylinder or a power screw positioned between the bearing housings to open or close the pairs of rolls. 